An example of the conventional exhaust devices for a diesel engine comprises a liquid-fuel supply source which supplies liquid fuel to a gas generator, which converts the liquid fuel to flammable gas as well as the present invention. A flammable-gas pipe led out of the gas generator is communicated with an exhaust-gas route on an upstream side of a diesel-particulate-filter. An oxidation catalyst is arranged upstream of this filter in the exhaust-gas route and the flammable gas is burnt with the oxidation catalyst to produce combustion heat that heats the exhaust gas. The thus heated exhaust gas burns the exhaust-gas fine particles remaining at the filter.
However, in the conventional exhaust device for a diesel engine, the flammable gas is burnt only with the oxygen contained in the exhaust gas, and besides no igniting means is provided. Therefore, it causes problems.